This article discusses how a social movement builds the identities, discourses and social relations through which it expresses its discontent with a government action. Analysis is based on Francesca Polleta's concept of free spaces, which allows us to understand the mechanism by which a group of actors can discuss and express their criticism, relate to others based on their identity, and the ways in which social places are constructed as expressions of protest. The work is based on the mobilization that occurred in Sonora, Mexico against the construction of an aqueduct.